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Cycle Mechanism for Storage Management Queue Compaction

IP.com Disclosure Number: IPCOM000080750D
Original Publication Date: 1974-Feb-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 3 page(s) / 41K

Publishing Venue

IBM

Related People

Brannon, TL: AUTHOR [+2]

Abstract

This Operating System Virtual Storage Management technique involves the use of queue elements located within the storage being managed. During normal execution, it is possible that these elements may be scattered over large ranges of storage, causing a fragmentation problem. An additional fragmentation problem may arise, due to the fact that these queue elements must be protected from accidental destruction by the problem program. Thus a queue element that requires a new protected page to be allocated during the execution of a job, could cause the partition to be fragmented into two smaller pieces.

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Cycle Mechanism for Storage Management Queue Compaction

This Operating System Virtual Storage Management technique involves the use of queue elements located within the storage being managed. During normal execution, it is possible that these elements may be scattered over large ranges of storage, causing a fragmentation problem. An additional fragmentation problem may arise, due to the fact that these queue elements must be protected from accidental destruction by the problem program. Thus a queue element that requires a new protected page to be allocated during the execution of a job, could cause the partition to be fragmented into two smaller pieces.

In addition, it is possible that the allocation of a new page of protected queue area (PQA), could result in the queue elements necessitated by its existence being placed within it. When the original reason for its allocation disappears, it will remain allocated containing nothing but queue elements describing its own existence.

Such a condition is shown in Fig. 1. Storage management has queue elements that describe which pages are allocated to problem program. Before PQA2 is allocated, only one queue element is required for this description. If PQA2 is not contiguous to PQA1, two elements are required to describe problem program space. If there is not enough space in PQA1 when PQA2 is allocated, the additional element (A) is put in PQA2. This problem can be eliminated by later compaction. If room becomes available in PQA1 and element A moved, PQA2 would be given back to the problem program area. Also, through this compaction process, all the queue elements in a PQA page containing nothing but queue elements may be moved, allowing reallocation of that page to problem program. Compaction Mechanism.

Compaction is triggered at the end of each job step. At this point, most storage within the partition is free and the problem conditions are most easily remedied.

The queues involved...